/**
 *
 * @param {*} func
 * @param {*} wait
 * @param {*} immediate
 */
function debounce (func, wait, immediate) {
  let timeout, args, context, timestamp, result
  const later = function () {
    // 据上一次触发时间间隔
    const last = +new Date() - timestamp
    // 上次被包装函数被调用时间间隔 last 小于设定时间间隔 wait
    if (last < wait && last > 0) {
      timeout = setTimeout(later, wait - last)
    } else {
      timeout = null
      // 如果设定为immediate===true，因为开始边界已经调用过了此处无需调用
      if (!immediate) {
        result = func.apply(context, args)
        if (!timeout) context = args = null
      }
    }
  }
  return function (...args) {
    context = this
    timestamp = +new Date()
    const callNow = immediate && !timeout
    // 如果延时不存在，重新设定延时
    if (!timeout) timeout = setTimeout(later, wait)
    if (callNow) {
      result = func.apply(context, args)
      context = args = null
    }
    return result
  }
}
/**
 *  Determine the days of the month
 * @param {年 Number} year
 * @param {月 Number} month
 */
function determineDays (year = 2019, month = 1) {
  const montharr = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
  const _year = Number(year)
  const _month = Number(month)
  if ((_year % 100 === 0 && _year % 400 === 0) || (_year % 100 !== 0 && _year % 4 === 0)) {
    montharr[1] = 29
  } else {
    montharr[1] = 28
  }
  return montharr[_month - 1]
}
export {
  debounce,
  determineDays
}
